Hardfacing rods are widely used for applying a hard surface, also known as a hardfacing, to a base material to protect the base material from abrasive wear and/or to provide a cutting surface thereon. These base materials are typically of a metal material and may be in the form of tools such as hand and power shovels, cutting tools, hammers, agricultural tools, down hole drill bits, etc.
A widely used type of such hardfacing rod incorporates hard particles, such as refractory carbides within a tubular metal rod. The hard particles are deposited from the hardfacing rods by thermal diffusion through the use of a high temperature gas flame, an electric arc, or a similar source of heat. Depending on the source of heat, the tube is characterized as a welding rod or as both a welding rod and an electrode. (For example, gas flame and electric arc, respectively.)
It will be appreciated that it is generally advantageous to minimize the amount of carbide particles dissolved in the weld pool and to suspend the carbide particles uniformly in the weld pool. Carbide particles that are undissolved and uniformly dispersed in the weld pool better perform their intended function of cutting and/or resisting abrasion. Accordingly, hardfacing rods should deposit as high a carbide content as possible to produce long wearing and/or cutting surfaces.
Various types of hardfacing rods are known. U.S. Pat. No. 2,280,223 discloses a coated hardfacing rod having a core of a hard alloy metal. The hard alloy metal core may be a high carbon containing cobalt and chromium or tungsten or both which may contain additions of nickel, molybdenum, tantalum, titanium, iron and cesium. The coating contains metal carbides. U.S. Pat. No. 2,507,195 discloses a hardfacing rod including an austenitic manganese steel in combination with carbide particles. The carbide particles may be formed as a coating and/or core on or in the rod. The austenitic manganese steel is added for its toughness and cold work properties. U.S. Pat. No. 3,023,130 discloses either a hardfacing rod of a stainless steel matrix composition having carbide particles within a flux coating on the outside of a rod or carbide particles within a flux coating within the rod.
Although there are various types of hardfacing rods known, further improvements on hardfacing rods are desired. One aspect of the present invention is to provide tubular arc hardfacing rods which are useful in depositing carbide containing wearing and/or cutting surfaces which are simple and economical to manufacture. It is an additional aspect of the present invention to provide arc hardfacing rods which will deposit a uniform dispersion of carbide particles within a weld pool.
It is a further aspect of the present invention to prevent excess solutioning of carbides and formation of brittle deposits. Still another aspect of the present invention is to produce arc hardfacing rods which will deposit a high proportion of carbide particles in a weld pool relative to the carbide particles comprising the rods.
A further aspect of the present invention is to provide commercially acceptable arc hardfacing rods in which there is a minimum interference due to slag under the arc, the smoke level is low enough to afford good visibility, the spatter level is low enough so that very little metal is lost to the air or other sections of the base material, there is minimum porosity in the deposit and the deposit is easily controlled by the welder.